Group , Poster #039, Ground Motions

Verification of the broadband CyberShake platform

Scott Callaghan, Christine A. Goulet, Fabio Silva, Philip J. Maechling, Robert W. Graves, Ossian O'Reilly, Kim B. Olsen, Te-Yang Yeh, Albert R. Kottke, & Yehuda Ben-Zion
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Poster Presentation

2021 SCEC Annual Meeting, Poster #039, SCEC Contribution #11384 VIEW PDF
SCEC has developed the CyberShake software platform to implement a physics-based probabilistic seismic hazard analysis (PSHA) approach using 3D wave propagation simulations to calculate seismograms and ground motions from sources defined in regional earthquake rupture forecasts. CyberShake has been used to calculate PSHA models for multiple regions in California, and is able to quantify effects such as 3D basin amplification and rupture directivity that are difficult to capture in conventional empirical ground motion models. Recently, CyberShake has been extended to generate broadband ground motions up to 50 Hz using a stochastic approach in order to include frequencies of engineering intere...st.

Broadband CyberShake has undergone an extensive verification effort, comparing with results from the SCEC Broadband Platform (BBP) using historical earthquakes such as Northridge. As part of the verification process, we generated broadband CyberShake ground motions by combining simulation results from deterministic finite difference wave propagation in 1D media (≤1 Hz) with stochastic high-frequency propagation (1-50 Hz) for simple fictitious events and historical events. We then compared the CyberShake ground motions to those computed with the BBP, which uses a frequency-wavenumber code for low-frequency content and a stochastic code for high-frequency content. We found close agreement in 1D simulations between the CyberShake and BBP results for ground motion time series, Fourier amplitude spectra, and pseudo-spectral accelerations across multiple sites.

We will present key verification results from the exercises above and will describe how CyberShake components were configured to support BBP validation events. We will then build on these results to propose modifications to CyberShake to improve its accuracy in ground motion modeling.

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